Ultimate 18' Tri ?

[Doug Lord]

I wrote a while back about a tri using an ama that rotated about it's longitudinal axis. The ama would have a shape such that one half the ama was a displacement hull with a length to beam ratio of 18-20/1 ;the other half was a stepped planing hull similar to Parlier's cat.
Rotatable Hull(ROH) Multifoiler - Boat Design Forums
Address:http://www.boatdesign.net/forums/showthread.php?t=10267&highlight=ROH+Trimaran
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My latest thoughts on this are to make the foils on the main hull fairly small and not to use them to lift the boat before ama rotation. As the boat begins to plane on the rotated stepped ama's the loading on the foils would be very low since their entire mission would now be pitch control only-not used specifically for early lift and not used to add RM.
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PS- the new stepped amas on Hydroptere are a shorter stockier version of what I have in mind-they do not rotate but their shape ROUGHLY illustrates the similar shape of the model I used to test this geometry.
All I need now is for someone to put up the 100 grand(more or less) to have Eric Sponberg engineer this thing and to build it.
I think this concept offers very high potential speed and sitting here looking at the remnants of Barry pass by sparked my thinking along these lines again...
This should bring you to a close up of the stepped ama's on Hydroptere.
Hydroptere
Address:http://www.hydroptere.com/index.php4?lang=EN
Now visualize this ama upside down and that would be the sub-planing attitude of my hull. Right side up when planing.

[frosh]

Hi Doug, You are right into my "territory" suggesting an 18ft. killer tri.
However I think that 100 grand might be the finishing price for subsequent boats, with the development of the prototype quite a bit higher.
Even if you had a sponsor with unlimited funds, which is so unlikely to ever happen as you would need a pure altruist. The market for such a machine I see as nil; even you could not come up with a convincing argument as to where paying clients would come from. The vaka with lifting foils could easily be a Moth foiler scaled up around 65% in all dimensions. This would give you a vaka of around 18ft. 2inch in length and max. beam of 20 inches. Is it going to be a single or doublehander?
Now you want a square configuration so lets say a beam of 18 ft. I guess the least expensive option here would be to purchase 100% carbon/epoxy tubing from a high tech specialist tube builder such CST composites. Even the building of the amas with a displacement shape such as that on a Hobie Tiger on one side, and then like Parlier's Hydraplaneur on the 180 degree opposite side, would not be insurmountable either, but definitely not easy. L/B ratios of the two configurations would probably need to differ for max efficiency. The displacement side obviously needing much more fineness generally, and forward sections with a wave piercing characteristic shape. Planing is far more efficient and earlier with lower L/B ratio, and very little fineness in hull shape after about 30% of the way behind the bow.
In my opinion we have now done the easy stuff, and the rest becomes incredibly challenging in an engineering sense.
I would guess that you would want a little more sail power than that provided for by a Hobie Tiger, as overall beam is huge and overall weight almost certainly higher than the Tiger. It will need to be a stayed rig in my opinion, but I could be wrong. If stayed, then it would definitely end up quite a bit lighter overall.
Staying points would be a little inboard of the outer ends of the crossbeam, to avoid impinging on the complex mechanism required to mount the crossbeam tube to the support that needs to rotate. What if the configuration of the mast step and crossbeam position do not correspond to a a sensible sweep back angle for the side stays? I can't begin to see how you could mount a chainplate on the rotating ama. On my amas the chainplates are mounted on the amas, exactly midway between the locations where the front and rear crossbeams intersect with the ama.
Possibly the unstayed option might be better, even with the weight penalty. Even so I can see that that the huge lateral forces on an unstayed mast on such a powerful 18 footer would probably disintegrate the hull around the position where the mast penetrates the vaka, when the breeze comes up.
What mechanism would be employed to rotate the amas 180 degrees? Maybe an electric motor? Weight, plus more weight for batteries. This will then need even more sail power than initial estimates. You then have to consider longitudinal stablity very carefully as a catastrophic pitchpole over the bows is starting to become quite a likely consequence in a decent breeze. Don't even go there, saying that this would be a single hander, and the rotation would be manual, requiring human muscle power.
What about the engineering behind the complex joints between amas and crossbeams. I have some doubts that even Eric Sponberg will be able to solve this one, in such a way that it would be capable of thousands of rotations on open water while the tri is moving, without breaking up. Don't bother with the entire project if the skipper has to decide before launching which configuration, displacement or planing, for the amas is the correct choice.
Honestly, even for you, I think that you have aimed far too high this time!

[Doug Lord]

Honestly, even for you, I think that you have aimed far too high this time!
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Why, thanks Frosh, I do my best. And thanks for your reply.
1)The rotation is only done at the as yet to be determined crossover point-not necessarily when the main hull flys(which will be at about 6-8knots boat speed max.) but when the planing hulls will work optimally.
2) Rotation will be manual and very simple and quick-it would not be frequently done at most venues.
3) Shrouds ,if any, will go outboard almost max(or where Eric says). I would like to look very carefuly at an unstayed highspeed rig like a Moth type(w/o the stays) as well as a wing rig for a speed version depending on weight. My realistic guestimate is that a partially stayed rig will be required.
4) Estimated upwind SA for this boat is 380sq.ft. compared to 227 for the Hobie Tiger. The Max RM for the 18 tri would be 10512 ft.lb vs 5197 ft.lb for the tiger-over TWICE the Hobie RM for the 18.
This is based on two crew of 160lb. each on trapezes with the 18 just flying the main hull and the cat just flying the windward hull.
5) The 18 would have 2lb/sq.ft. sail loading vs 3.15 for the Tiger.
6) The Hobie weighs 397 lb. and is fiberglass/foam sandwich and this boat would be 100% carbon foam/honeycomb and a very rough estimate of weight would be all up at 447lb.
7) Eric Sponberg is one of the premier naval archtects and marine engineers in the world today and he would do an exemplary job on this boat.
8)The boat could be "toned down" substantially and still beat most beach cats. The idea here is to illustrate what is possible with the trimaran configuration. One of the central themes of the 18 are the small hydrofoils on the daggerboard and rudder-FOR PITCH CONTROL ONLY. This,and the fact that the center of buoyancy moves forward when the ama's are planing will give the boat extraordinary resistance to pitchpoling.

[Chris Ostlind]

Hey, it's your money...

Funny part of all this is, you could get beach cat killer performance out of an 18' tri by simply building the boat light and strong, not using any failure prone rotating anythings and sailing it well. None of the trick stuff is necessary. Just simply done, well-proven parts and design layouts that are executed nicely.

The Nitro trimaran out of France, http://www.navaldesigner.com/en/index.html (in the Gallery section)
has already done all the, flying the main hull, stuff from a compact design of 4.6 meters LOA and it used no trick anything in the way of rotating parts. If the builder would simply install a bigger rig, spread the beam just a bit and put her back in the water, you'd have the tri that could kill any beach cat under 20' that is out there. So, you are blazing what new trail here with this overly-complicated design idea?

What is it that makes people think they are advancing the craft when they toss yet more complicated mechanisms into the mix? How about something like a thought-through design concept that actually simplifies the whole potential of a given design idiom so that more people can enjoy the potential rather than a self-limiting smaller number due to complexity?

Chris

[Doug Lord]

Actualy, the ROH system is quite simple and robust and with a potential of 40+% less drag at planing speeds offers quite high top end speed-much higher than available thru a "normal" displacement hull multihull. And with none of the low and medium speed problems associated with Parliers cat. The combination of planing ama's and the use of relatively lightly loaded foils for pitch control offers unmatched pitch stability for a multihull of this size.
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Thanks for the Nitro-looks good. But I can't find any specs anywhere.....

[frosh]

Hi Doug, you might think that you have some talent with misuse and twisting of the English language to suit your purposes.

Originally Posted by frosh
Honestly, even for you, I think that you have aimed far too high this time!
Well thanks Frosh---- QUOTE- Doug Lord.

I think that you have been well and truly trumped.
Go check out your/mine latest posting re Chris Oslind's latest S & G tri in the Design section. Happy reading!

[frosh]

Jeez- Doug, I expected a massive response by now. What has happened to the big man with so much to say? :confused:

[Doug Lord]

I've gotten into doing more research on small tris in the size range of the previous post. I think I know most of the existing designs and concepts but in case I don't: is anybody familiar with any designs or serious concepts for beachcat killer tris around 18' LOA,square or oversquare overall length to beam ratio, with or without foil assist and designed to fly the main hull?
I know about the Exploder which is the only true "mini ORMA" type that I'm familiar with but it's 23'. I want to see if I've missed something in real high performance tri design in the vicinity of 18'.
Thanks in advance for any leads....

[Darryl Barrett]

try this one

[Doug Lord]

which one-your link doesn't appear to work

[Darryl Barrett]

Try that now. It is 4.3m long for the centre hull and ALL up sailing weight is less than 60kg, the "plug" is in the final stages of completion as I wright

[Doug Lord]

Darryl, the numbers sound exciting but I have web tv and can't open your file. Is this a foiler tri? Could you post a j-peg (or send me one or more ) - lorsail@webtv.net
Can you post more numbers? Thanks....

[Darryl Barrett]

Try that now. It is 4.3m long for the centre hull and ALL up sailing weight is less than 60kg, the "plug" is in the final stages of completion as I write

[frosh]

Actualy, the ROH system is quite simple and robust. QUOTE - DOUG LORD.

Yeah and how is it done? Or do you think that you can make a claim like that and no-one will ever ask you to back it up. I challenge you to show the evidence that it is both simple and robust. Any refusal to post an answer to this challenge will taken as an "I don't really know anything about this, I just wanted to impress everyone that I had a firm grasp on the design concept, when in fact I had not a clue".

[frosh]

Hi Darryl, your 4.3m foiler tri looks very interesting. What are the more complete specifications including rig and details of the foils. On what do you base that the finished product will actually sail as per your own design brief? This is not intended in any way to denigrate the design, but merely to ask if you have based your concept closely on any other sucessful sail boats.
Regards, and best of luck. Sam

[Doug Lord]

Actualy, the ROH system is quite simple and robust. QUOTE - DOUG LORD.

Yeah and how is it done?
On the 18 it would be done by removing a pin, rotating the hull by hand, and then reinserting the pin. It could also be done by using a gear drivebelt and pin. The rotating structure itself would be engineered so that the hull had the same longitudinal bending strength as a normal hull. This would result in slightly more weight than a normal hull but that is offset by the smaller size(and volume) of the whole ama(as compared to a displacement ama).

[frosh]

On the 18 it would be done by removing a pin, rotating the hull by hand, and then reinserting the pin. QUOTE- DOUG LORD

OK it could be done be two guys on the shore, but on the water this would be impossible or at a minimum the stuff of legends. If you have been out on a short board sailboard in strong winds and you suffer a rig from hull separation which is not all that uncommon, the subsequent seemingly very simple re-assembly required to save one's self and get back to the beach requires exhausting and almost super human effort in rough water. But guess what? the motivation to fix it and save you self is an over whelmingly huge motivation.

[Darryl Barrett]

Well, I have been designing, building, sailing, and successfully selling commercially, my high performance catamarans now for over 40 years, and over that time I have never produced any multihull that did not actually exceed its design brief! The last cat that I designed and produced is the Alpha Omega F14 which has now shown to be the fastest 14’ cat in the world and they compete “head to head” for “across the line first wins” against much larger cats such as the NACRA 5.8, A class, formula 18’s, F16’s, etc, etc. The all up sailing weight of the Alpha Omega F14 is 75kg and this foiling tri is based on the centre hull being from and Alpha F14, The foils I have been studying and working on for over 40 years, The Alpha F14 already sails with “T” foils on the bottom of the rudders which have proven to be very advantageous to it’s performance.

[frosh]

Hi Darryl, You have made very very big claims for the alpha omega 4.3 cat. being quicker that A cats at times etc. etc. Easy to say on a forum, where are some results that are convincing? Also I asked in my posting #15 to give more specifications. Your sketch (schematic only?) in your posting is so rudimentary as to convey almost no information. Can we get some more details of the new tri design?
Regards, Sam

[Darryl Barrett]

I see that you are in Australia? And you have not heard of the performance of the Alpha Omega F14??? Just look up the Yachting Victoria web site and have a look at the YA yardstick for the F14 in comparison to the other cats mentioned then come back and resume your cynicism. Just where in Aust’ are you if you haven’t hear about the performance of the AO F14?
Do you or don’t you sail? Is all that you talk about here confined to “theory” with no actual practical experience??? Do a little research on my name and the 5000 odd multihull craft that I have designed, manufactured and sold throughout Australia over the last 40 odd years, then come back and ask some appropriate questions instead of attempting to cast aspersions.

[Doug Lord]

Darryl, as I've said before your boat looks very interesting. I have some questions:
1) Why four hydrofoils? One of the big advantages of the bifoiler configuraton, as you know, is the ability to heel the boat to weather to unload the vertical fin. Would something like that be possible with your configuration? I've always been taught that surface penetrations in a hydrofoil design should be minimized-and you have four-what is your theory?
2) Do the outboard foils generate righting moment? How do you control altitude?
3) Why did you choose swept foils; isn't there an efficiency penalty for that much sweep?
4) How much sail area do you envision?

[frosh]

Darryl, You have a manner about you that is somewhat odious and with an air of supremacy which comes across very strongly. I have been sailing for 41 years and my first boat, something similar to the original Sailfish design, was self designed and built, and was a very successful one off. Since then I have sailed in Intervarsity Lightweight Sharpies, Skates, Moths and extensively in sailboards. I have been published in 'Windsurfing Magazine" out of the USA in March 2002 (page 22). It is feature article with large photo published in the section of the mag entitled LEADING EDGE.
What is being featured is a 20ft. tandem high performance sailboard being sailed by me and my son. This is a unique design and constuction for a sailboard.
I have never owned a catamaran although have sailed on them at times including the Tornado. I have not found catamarans to my taste as sailboat I want to own.
By the way, I have lived in Perth for many years, and do most of my sailing on the Swan River, but have raced and windsurfed on the Indian Ocean many times as well.
I am not going to go on about this stuff, as after almost 600 postings on this forum I have hardly ever blown my own trumpet until now.
I only asked you a couple of normal questions, to which you could have graciously provided the requested information. Now I suggest you go and think about your response and try again later.

[Darryl Barrett]

Well, thank you for your comments as to your assessment of my “attitude”, “Frosh” read and noted.
To answer your queries DL.
There are only three lifting foils, one at the bow of the centre hull and one each at the extremities of each ama. The foil on the rudder is a pre set, parallel to the average water level, “T” foil and its sole purpose is as a pitch control, although its function is somewhat negated by having three automatically adjustable lifting foils I still like it for that pitch control function. I think what you are referring to by “the ability to heel the boat to weather to unload the vertical fin”, is something that may be applicable to something like the Moth supported on a single central main foil (and to a lesser degree the single asymmetrical rudder foil) than it is to this type of foiler where the pitch and heel all come under the influence of a dramatically larger support “base”
All three lifting foils are symmetrical (as opposed to “wing” like asymmetrical) and they are all controlled independently by a “wand”, meaning that all are capable of positive lift either upwards or downwards which ever is appropriate depending on the height that the craft is airborne and its “roll” or as you say “heel” attitude. The object of a high performance foiler is to have as little heel as possible as heel would indicate a greater difference than desired between the lift being generated by the sails and the speed of the craft across the water, so yes the outboard foils generate “righting” moments (as does the centre foil as well when the leeward foil generates enough lift to support the entire load of the craft and them some) angled or raked foils are more efficient when it comes to foil cavitation prevention and as well as for other reasons, they automatically shed weed and a foil when raked for all intents and purposes becomes a much higher aspect ratio foil than when straight as it exposes a much greater length to the direction of the water that it is travelling through with the same chord height. The entire foil rotates not just a trailing flap so giving them great directional controllability of lift as well as increasing the efficiency of lift generation (either up or down) greatly over fixed foils with trailing flaps. (Particularly asymmetric foils)
This craft carries a 25’ rotating carbon fibre mast and is cat rigged with a mainsail area of 13 sqm (including half the area of the mast bounded by the luff length of the main sail) and an 11sqm spinnaker.

[Darryl Barrett]

These are the "plugs" that the molds were made from for the adjustable foils and the second is a photo of the T foil rudder already in use on the Alpha Omega F14
The third is a photo of an Alpha Omega F14, this has the same rig and sail plan as the foiler and the centre hull of the foiler is the same hull (finished weight per hull 15.5kgs)

[frosh]

Thanks Darryl, now I think we can be friends and exchange ideas for our mutual benefit. Looks very very good. Please keep us informed with photos and info. as you make progress.
Regards, Sam

[Doug Lord]

The "ROH" hull referenced in the first post of
this thread is shown in rough model form here-second row down:
X21
Address:http://www.monofoiler.com/x21.html Changed:12:38 PM on Friday, September 21, 2007
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The model shows the concept in both displacement and stepped planing hull configurations. These are the same model with the hull simply rotated. The idea is to be able to sail on the displacement hull until the right speed is reached to rotate both amas and effectively utilize the stepped planing hull configuration. The windward ama is rotated first then the boat is tacked and the other one rotated. Should conditions change to where the planing hull is not suitable the process can be reversed back to the displacement hull(L/B=20/1). It is envisioned that the process would be very quick-less than 3 minutes. The concept is actually going to be tried in about a year or so on my experimental X21-T. See that thread under "sailboats". As mentioned in the earler part of this thread the ROH concept depends on the use of two fairly small hydrofoils on the main hull daggerboard and rudder-primarily for pitch control.

[Chris Ostlind]

Nice to see some photos of the work in progress, Doug. You'll potentially engender so many positive outside contributions to your effort by exhibiting it in this fashion.

There is potential in this approach, but there are also a mountain of technical issues to solve if it is going to proceed to functional fulfillment.

What is going to ensure that water flow over the displacement surface is not disrupted by the "slots" for the rotating mechanism? Isn't the drag associated with this tranverse slot going to hamper the potential to get the boat up to speed where the possibility of a planing surface can be of an advantage?

How are you going to waterproof the pivot point in the hull to avoid the entry of high pressure water?

In the foiling model, you show the mast stepped well forward and the drawings show it in a more conventional location? Which is it going to be on the full sized craft? If it is well forward, what has been done to the Hobie hull to resist torsional loading into the structure that far forward?

Other questions to follow.

Good luck with the process.

Chris

[Doug Lord]

Thanks ,Chris. The ROH model was done to allow me to visualize the geometry of the concept and it has potential but there are problems that need to be solved experimentally-on the X21-T platform. I think the seam can be worked out to be virtually no problem but time will tell.
The little red model is of the aeroSKIFF™ 14 and it has much more rake than does the X21 so the mast is further forward.You can see the first sketches of it done by Eric Sponberg on the original Peoples Foiler thread...The rough sketches posted as of this date show the X21-T -not the aeroSKIFF™.
The X21-T will have a carbon tube structure to reinforce the standard Hobie hull and may have an additional 45/45 layer of 5.7oz carbon inside and out-not finalized yet. But the preferred system is to use the tubular structure to take the mast loads.

[Doug Lord]

The "ROH" hull referenced in the first post of
this thread is shown in rough model form here-second row down:
X21
Address:http://www.monofoiler.com/x21.html Changed:12:38 PM on Friday, September 21, 2007
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The model shows the concept in both displacement and stepped planing hull configurations. These are the same model with the hull simply rotated. The idea is to be able to sail on the displacement hull until the right speed is reached to rotate both amas and effectively utilize the stepped planing hull configuration. The windward ama is rotated first then the boat is tacked and the other one rotated. Should conditions change to where the planing hull is not suitable the process can be reversed back to the displacement hull(L/B=20/1). It is envisioned that the process would be very quick-less than 3 minutes. The concept is actually going to be tried in about a year or so on my experimental X21-T. See that thread under "sailboats". As mentioned in the earler part of this thread the ROH concept depends on the use of two fairly small hydrofoils on the main hull daggerboard and rudder-primarily for pitch control.

And here are a couple of pictures that illustrate the concept with a rough balsa model: